However, the leftist opposition is split between two leading candidates in a technical draw, and it likely that Pinera would face a tougher challenge in a probable second round run-off in December.

When asked who they would like as the next president of Chile, 32 percent of respondents in the GfK Adimark monthly poll named 67-year-old Pinera, who previously led the country between 2010 and 2014 and is favored by the business community for his emphasis on pro-economic growth proposals.

The Frente Amplio derives much of its support from young, urban Chileans who are seeking a sharp change of direction for the country, which is widely seen as one of Latin America's success stories but has struggled to address issues with inequality and poor education outcomes.

Guillier, who entered politics in 2013, also paints himself as an outsider, but has lost momentum in recent months. His policy direction of more moderate tweaks to the economic model of the top copper exporter has largely echoed that of incumbent President Michelle Bachelet, and he is supported by the majority of parties in Bachelet's Nueva Mayoria bloc.

Other polls have suggested a second round December vote would be close, but that Pinera would likely secure a narrow victory against either Sanchez or Guillier.

Bachelet, whose approval rating has crept up in her last year in office, to reach 32 percent in Wednesday's poll, is constitutionally barred from running for a consecutive term.

The poll surveyed 1,050 people between July 4 and July 26, with an error margin of 3 percentage points.